Recent deregulation of the telephone companies requires that all premises wiring be customer owned and that the serving telephone company provide a network interface device separating the company's wiring from the customer's wiring. The Electronic Industries Association recommends that a device be provided for connecting single-line service, and that two-line service should be provided at the network interface as two single-line services. The device should be foolproof and is intended to provide a means for isolating troubles between terminal equipment, premises wiring, and public network facilities. The device should provide a standard RJ11 jack for testing purposes, and should be weatherproof for outside mounting.